The effect of cluster density on the penetration depth of an energetic large gas cluster impinging on a silicon target

Abstract

Large accelerated gas clusters are being increasingly employed in a number of different surface treatment and analysis schemes, from semiconductor doping, through surface smoothing to the probing beam for secondary ion mass spectrometry (SIMS). Although the use of such clusters is finding great new application and providing potentially new and exciting capabilities in materials processing and analysis some of the effects of key parameters in the process are less understood and inadequately studied. The gas clusters are normally created by an aerosol effect in which droplets rapidly expand after passing through a fine nozzle and cool quickly and form frozen droplets. The precise density of the frozen droplets is not well known and it is possible that the clusters could have a density ranging from a perfect solid packing solid density to that of a frozen gas. The work presented here uses molecular dynamics computer simulation to investigate the likely effect that changes in the cluster density will have on the processing properties of large argon gas clusters. In particular it is found that the penetration depth of the energy deposited by the cluster is dependent upon the cluster density.